Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
In typical cellular wireless networks, user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices subscribe to service from a given cellular wireless service provider. In practice, a service provider will operate one or more networks (sometimes referred to as radio access networks (RANs)) including base stations that radiate to define wireless coverage areas in which the UEs can operate.
Through each base station (and corresponding RAN), a UE can obtain connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. Each RAN may include one or more radio network controllers (RNCs), mobility management entities (MMEs), or the like, which may be integrated with or otherwise in communication with the base stations, and which may include or be in communication with a switch or gateway that provides connectivity with the one or more transport networks. With this arrangement, a UE within coverage of a RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
In general, a cellular wireless network may operate in accordance with a particular air interface protocol or radio access technology, with communications from the base stations to UEs defining a downlink or forward link and communications form the UEs to the base stations defining an uplink or reverse link. Each of these links may be structured to define particular channels on which certain types of data may be transmitted.
The forward link, for example, may define: (i) a pilot channel on which the RAN may broadcast a pilot signal to allow UEs to detect wireless coverage, (ii) system parameter channels (e.g., an overhead channel) on which the RAN may broadcast system operational parameters for reference by UEs so that the UE can then seek network access, (iii) paging channels on which the RAN may broadcast page messages to alert UEs of incoming communications, and (iv) traffic channels on which the RAN may transmit bearer traffic (e.g., application data) for receipt by UEs. The reverse link, for example, may define: (i) access channels on which UEs may transmit “access probes” such as registration messages and call origination requests, and (ii) traffic channels on which UEs may transmit bearer traffic for receipt by the RAN. These channels may be defined through the use of various mechanisms, including for example, time division multiplexing, code division multiplexing (e.g., spread-spectrum modulation), frequency division multiplexing, as well as others.
When a cellular wireless network seeks to page a UE for an incoming call or for some other reason, an MME or switch in the network may send a page message to numerous base stations in the MME or switch's coverage area, with the hope that the UE will receive a page message broadcast by a base station, and the UE will respond. To carry out a page, the MME or switch may transmit some indication of the reason for the page (e.g., that there is an incoming call or data packed directed to the UE) to each of the numerous base stations that the MME or switch sends a page message. In turn, each base station may use this indication to generate a page record, which the base station may transmit to the UE in one way or another. The UE may then reply to one of the base stations with a page-response message (PRM), or some other message indicating successful receipt of the page record.
In operation, a cellular wireless network may implement a “zone-based” paging scheme. In such a scheme, the base stations in the RAN are divided into tracking areas, each with a respective tracking area identity (TAI). To facilitate paging on a zone basis, each base station in the RAN may broadcast as one of its overhead parameters the TAI for the tracking area in which the base station is included. A UE operating in the network may then programmatically monitor the TAI(s) specified in the overhead messages and may register with the network by, for example, transmitting to the RAN a tracking area update (TAU) message when the UE detects that it has moved into a new tracking area (or for other reasons). With this process, registration records maintained by a RAN entity (e.g., an MME or a switch) will indicate the tracking area in which each UE last registered. When the RAN seeks to page a certain UE, the RAN entity may then refer to the registration records to determine which base station(s) to send a page message to in accordance with a particular paging strategy.
Using an example paging strategy that is implemented in many cellular wireless networks, for instance, the network may make up to three attempts to page a UE that last registered with a particular base station. In particular, the network may first attempt to transmit a page record to the UE using the particular base station (i.e., the particular base station would transmit the page record). Then, if the first attempt is unsuccessful (i.e., the UE does not acknowledge the page record), the network may make a second attempt to page the UE by transmitting the page record in a tracking area in which the UE is registered (i.e., each of the base stations in a tracking area in which the UE is registered would transmit the page record). If the second attempt also fails, then the network may make a third attempt to page the UE, possibly with a system-wide transmission of the page record (i.e., in all tracking areas served by the MME or switch that serves the tracking area in which the UE last registered), although it is possible that a third attempt may be of a different scope as well.